Buggy code:
public class Composite extends Scrollable { Layout layout ; Control [ ] tabList ; int scrolledVisibleRgn ; int siblingsVisibleRgn ; int layoutCount = 0 ; Composite ( ) { } public Composite ( Composite parent , int style ) { } Control [ ] _getChildren ( ) { } Control [ ] _getTabList ( ) { } int callFocusEventHandler ( int nextHandler , int theEvent ) { } public void changed ( Control [ ] changed ) { } public Point computeSize ( int wHint , int hHint , boolean changed ) { } protected void checkSubclass ( ) { } Control [ ] computeTabList ( ) { } void createHandle ( ) { } void createHandle ( int parentHandle ) { } void createScrolledHandle ( int parentHandle ) { } void drawBackground ( int control , int context ) { } void enableWidget ( boolean enabled ) { } Composite findDeferredControl ( ) { } void fixTabList ( Control control ) { } public Control [ ] getChildren ( ) { } int getChildrenCount ( ) { } public Layout getLayout ( ) { } public boolean getLayoutDeferred ( ) { } public Control [ ] getTabList ( ) { } int getVisibleRegion ( int control , boolean clipChildren ) { } int kEventControlClick ( int nextHandler , int theEvent , int userData ) { } int kEventControlGetFocusPart ( int nextHandler , int theEvent , int userData ) { } int kEventControlSetFocusPart ( int nextHandler , int theEvent , int userData ) { int result = super . kEventControlSetFocusPart ( nextHandler , theEvent , userData ) ; if ( result == ( OS . noErr ) ) { if ( ( ( state ) & ( CANVAS ) ) != 0 ) { if ( ( scrolledHandle ) != 0 ) { if ( ( ( ( style ) & ( SWT . NO_FOCUS ) ) == 0 ) && ( hooksKeys ( ) ) ) { short [ ] part = new short [ 1 ] ; OS . GetEventParameter ( theEvent , kEventParamControlPart , typeControlPartCode , null , 2 , null , part ) ; if ( OS . HIVIEW ) { <START_BUG> OS . HIViewSetNeedsDisplay ( scrolledHandle , true ) ; <END_BUG> } else { drawFocusClipped ( scrolledHandle , ( ( ( part [ 0 ] ) != ( OS . kControlFocusNoPart ) ) && ( drawFocusRing ( ) ) ) , hasBorder ( ) , getParentBackground ( ) , inset ( ) ) ; } } } } } return result ; } int kEventMouseDown ( int nextHandler , int theEvent , int userData ) { } int kEventRawKeyPressed ( int nextHandler , int theEvent , int userData ) { } int kEventUnicodeKeyPressed ( int nextHandler , int theEvent , int userData ) { } boolean hooksKeys ( ) { } void invalidateChildrenVisibleRegion ( int control ) { } public boolean isLayoutDeferred ( ) { } boolean isTabGroup ( ) { } public void layout ( ) { } public void layout ( boolean changed ) { } public void layout ( boolean changed , boolean all ) { } public void layout ( Control [ ] changed ) { } void markLayout ( boolean changed , boolean all ) { } Point minimumSize ( int wHint , int Hint , boolean changed ) { } void releaseChildren ( boolean destroy ) { } void releaseWidget ( ) { } void removeControl ( Control control ) { } void resetVisibleRegion ( int control ) { } int setBounds ( int x , int y , int width , int height , boolean move , boolean resize , boolean events ) { } public boolean setFocus ( ) { } public void setLayout ( Layout layout ) { } public void setLayoutDeferred ( boolean defer ) { } boolean setScrollBarVisible ( ScrollBar bar , boolean visible ) { } boolean setTabGroupFocus ( ) { } public void setTabList ( Control [ ] tabList ) { } int traversalCode ( int key , int theEvent ) { } void updateLayout ( boolean all ) { } }

Fix:
redrawWidget ( scrolledHandle , false ) ;